queueconsumerendpoint.java

来自「OpenJMS是一个开源的Java Message Service API 1.」· Java 代码 · 共 172 行

/**
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 *
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 *    copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the
 *    above copyright notice, this list of conditions and the
 *    following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. The name "Exolab" must not be used to endorse or promote
 *    products derived from this Software without prior written
 *    permission of Exoffice Technologies.  For written permission,
 *    please contact [e-mail].
 *
 * 4. Products derived from this Software may not be called "Exolab"
 *    nor may "Exolab" appear in their names without prior written
 *    permission of Exoffice Technologies. Exolab is a registered
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 *
 * 5. Due credit should be given to the Exolab Project
 *    (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2001-2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: QueueConsumerEndpoint.java,v 1.3 2005/08/30 05:30:52 tanderson Exp $
 */
package org.exolab.jms.messagemgr;

import javax.jms.InvalidSelectorException;
import javax.jms.JMSException;

import org.exolab.jms.message.MessageImpl;


/**
 * A {@link ConsumerEndpoint} for queues. This object shares access to a
 * particular queue with other QueueConsumerEndpoint instances.
 *
 * @author <a href="mailto:[e-mail]">Jim Alateras</a>
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.3 $ $Date: 2005/08/30 05:30:52 $
 */
public class QueueConsumerEndpoint
        extends AbstractConsumerEndpoint {

    /**
     * The destination that this consumer subscribes to.
     */
    private final QueueDestinationCache _cache;


    /**
     * Construct a new <code>QueueConsumerEndpoint</code>.
     *
     * @param consumerId the identity of this consumer
     * @param cache      the cache to register with
     * @throws InvalidSelectorException if the selector is not well formed
     * @throws JMSException             if the destination cache can't be
     *                                  created
     */
    public QueueConsumerEndpoint(long consumerId, QueueDestinationCache cache,
                                 String selector)
            throws InvalidSelectorException, JMSException {
        super(consumerId, cache.getDestination(), selector, false);

        cache.addConsumer(this);
        _cache = cache;
    }

    /**
     * Return the number of unsent messages.
     *
     * @return the number of unsent messages
     */
    public int getMessageCount() {
        return _cache.getMessageCount();
    }

    /**
     * This event is called when a non-persistent message is added to a
     * <code>DestinationCache</code>.
     *
     * @param handle  a handle to the added message
     * @param message the added message
     * @return <code>true</code> if the listener accepted the message; otherwise
     *         <code>false</ode>
     */
    public boolean messageAdded(MessageHandle handle, MessageImpl message) {
        // notify the consumer
        notifyMessageAvailable();
        return true;
    }

    /**
     * This event is called when a persistent message is added to the
     * <code>DestinationCache</code>.
     *
     * @param handle  a handle to the added message
     * @param message the added message
     * @return <code>true</code>
     */
    public boolean persistentMessageAdded(MessageHandle handle,
                                          MessageImpl message) {
        return messageAdded(handle, message);
    }

    /**
     * This event is called when a message is removed from the
     * <code>DestinationCache</code>.
     *
     * @param messageId the identifier of the removed message
     */
    public void messageRemoved(String messageId) {
        // no-op
    }

    /**
     * This event is called when a message is removed from the
     * <code>DestinationCache</code>
     *
     * @param messageId a handle to the removed message
     */
    public void persistentMessageRemoved(String messageId) {
        // no-op
    }

    /**
     * Return the next available message to the client.
     *
     * @return the next message, or <code>null</code> if none is available
     * @throws JMSException for any error
     * @param cancel
     */
    protected MessageHandle doReceive(Condition cancel) throws JMSException {
        MessageHandle handle = _cache.getMessage(getSelector(), cancel);
        if (handle instanceof QueueConsumerMessageHandle) {
            // associate the handle with the consumer
            ((QueueConsumerMessageHandle) handle).setConsumerId(getId());
        }

        return handle;
    }

    /**
     * Closes this endpoint.
     */
    protected void doClose() {
        // unregister from the DestinationCache
        _cache.removeConsumer(this);
    }

}